tools/power/turbostat: bugfix "--show IPC"

turbostat --show IPC

displays "inf" for the IPC column

turbostat was missing the explicit dependency of IPC on APERF,
and thus neglected to collect APERF when only IPC was requested.

typcial use:

turbostat --quiet --show CPU,IPC

Signed-off-by: Len Brown <len.brown@intel.com>